Thursday, 1 October 2015

calculus - Reduction formula of primitive big(1sin3xbig)ncosx




I am trying to obtain a reduction formula for π/20(1sin3x)ncosxdx

where nN. My attempt is as follows let v=sinxdv=(cosx)dx
The integral then becomes 10(1v3)ndv
By parts3n10v3(1v3)n1dv
But I can't get it in the form originally to have the integral exactly the same but in terms of n1. Thanks in advance.


Answer



Continuing from where you left:
In=3n10v3(1v3)n1dv=3n(10(1v3)n1dv10(1v3)ndv)


In=3n(In1In)In=3n3n+1In1


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